Mercurial > cpython-lru_cache-weakref
diff Lib/struct.py @ 44446:8d69edd3d290 legacy-trunk
Finish-up the struct module optimizations started at the Iceland NFS sprint.
| author | Raymond Hettinger <python@rcn.com> |
|---|---|
| date | Fri, 04 Jan 2008 00:01:15 +0000 |
| parents | 4aed4367add2 |
| children | 7643a43f25a1 |
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--- a/Lib/struct.py Thu Jan 03 23:54:04 2008 +0000 +++ b/Lib/struct.py Fri Jan 04 00:01:15 2008 +0000 @@ -1,99 +1,1 @@ -""" -Functions to convert between Python values and C structs. -Python strings are used to hold the data representing the C struct -and also as format strings to describe the layout of data in the C struct. - -The optional first format char indicates byte order, size and alignment: - @: native order, size & alignment (default) - =: native order, std. size & alignment - <: little-endian, std. size & alignment - >: big-endian, std. size & alignment - !: same as > - -The remaining chars indicate types of args and must match exactly; -these can be preceded by a decimal repeat count: - x: pad byte (no data); c:char; b:signed byte; B:unsigned byte; - h:short; H:unsigned short; i:int; I:unsigned int; - l:long; L:unsigned long; f:float; d:double. -Special cases (preceding decimal count indicates length): - s:string (array of char); p: pascal string (with count byte). -Special case (only available in native format): - P:an integer type that is wide enough to hold a pointer. -Special case (not in native mode unless 'long long' in platform C): - q:long long; Q:unsigned long long -Whitespace between formats is ignored. - -The variable struct.error is an exception raised on errors. -""" -__version__ = '0.1' - -from _struct import Struct, error - -_MAXCACHE = 100 -_cache = {} - -def _compile(fmt): - # Internal: compile struct pattern - if len(_cache) >= _MAXCACHE: - _cache.clear() - s = Struct(fmt) - _cache[fmt] = s - return s - -def calcsize(fmt): - """ - Return size of C struct described by format string fmt. - See struct.__doc__ for more on format strings. - """ - try: - o = _cache[fmt] - except KeyError: - o = _compile(fmt) - return o.size - -def pack(fmt, *args): - """ - Return string containing values v1, v2, ... packed according to fmt. - See struct.__doc__ for more on format strings. - """ - try: - o = _cache[fmt] - except KeyError: - o = _compile(fmt) - return o.pack(*args) - -def pack_into(fmt, buf, offset, *args): - """ - Pack the values v1, v2, ... according to fmt, write - the packed bytes into the writable buffer buf starting at offset. - See struct.__doc__ for more on format strings. - """ - try: - o = _cache[fmt] - except KeyError: - o = _compile(fmt) - return o.pack_into(buf, offset, *args) - -def unpack(fmt, s): - """ - Unpack the string, containing packed C structure data, according - to fmt. Requires len(string)==calcsize(fmt). - See struct.__doc__ for more on format strings. - """ - try: - o = _cache[fmt] - except KeyError: - o = _compile(fmt) - return o.unpack(s) - -def unpack_from(fmt, buf, offset=0): - """ - Unpack the buffer, containing packed C structure data, according to - fmt starting at offset. Requires len(buffer[offset:]) >= calcsize(fmt). - See struct.__doc__ for more on format strings. - """ - try: - o = _cache[fmt] - except KeyError: - o = _compile(fmt) - return o.unpack_from(buf, offset) +from _struct import *
